Plasma etching has been used for etching a film made of a semiconductor material in manufacturing electronic devices. A workpiece may be exposed to processing gas plasma so as to etch a film to be etched physically and chemically in plasma etching.
Further, an electronic device may include a film made of a hard-to-etch material, and the hard-to-etch material is needed to be patterned by the plasma etching as well. For example, an MRAM element provided with a film containing cobalt (Co) and palladium (Pd) (hereinafter, referred to as “CoPd film”) as a kind of a hard-to-etch material is described in Japanese Patent Laid-Open Publication No. 2011-14881. Further, an etching method in which plasma of a mixed gas containing a hydrocarbon gas and an inert gas is generated, a temperature of the CoPd film is set to 250° C. or less, and ions are attracted onto the CoPd film to etch the CoPd film is described in Japanese Patent Laid-Open Publication No. 2011-14881.
As described in Japanese Patent Laid-Open Publication No. 2011-14881, the CoPd film is patterned by the so-called ion sputter etching. However, the hard mask used in etching of the CoPd film has a low selectivity for the ion sputter etching of the CoPd film. Accordingly, verticality of a lateral surface of the hard mask during a time period until etching of the CoPd film is completed is remarkably reduced in the method described in Japanese Patent Laid-Open Publication No. 2011-14881. Further, constituent materials of the film having been sharpened by the ion sputter etching are reattached to the hard mask and a lateral surface of the film formed by the etching.
Therefore, a technique in which a film containing cobalt and palladium may be etched while suppressing degradation of verticality of a lateral surface of a hard mask and a deposit reattached to a workpiece is removed is needed in the present technical field.